Internal combustion engines generate power by combusting a mixture of a fuel and air. In some cases, the combustion process may result in formation of nitrogen oxides (NOx) among other gases, particulates in an exhaust. The NOx is considered as a pollutant. Therefore, vehicles or machines fitted with the internal combustion engines have to comply with regulatory emission standards that limit an amount of NOx in the exhaust generated by the engine. As such, it is essential to monitor the amount of NOx in the engine and accordingly control operations of the engine based on the amount of NOx. Various methods are proposed for determining the amount of NOx. One such method includes using a NOx sensor for determining the amount of NOx. However such implementation is costly. Additionally, the operating conditions within the machine may sometimes render the sensors faulty.
For reference, U.S. patent publication No. 2004/0144082 relates to a controller for controlling nitrogen oxides (NOx) emissions from a combustion engine based on estimating a parameter for the engine. The controller is capable of adjusting cylinder temperature based on the estimated parameter for controlling NOx emissions.